Friday, May 27, 2005

Are we designed for violence?

Violence is common to our present, history and prehistory. Is there reason to hope that our future will be different? Doubtless we’ll know in the long run, thanks to the grand uncontrolled experiment of life. Meanwhile some argue we can get an early forecast by using the behavioural sciences – investigate our nature to divine our future. But just what do we mean by a violent nature, and would such a nature necessarily force us to be so pessimistic? Such a wide issue needs to be viewed through a narrow prism, so here we shall focus on the neuroscience of violence. Are we wired for violence - is it brain-based, an original sin never to be expelled? Or could it be less indelible than we fear?

While examples of human violence are varied and plentiful, the most chilling are those individuals who seem innately disposed towards causing suffering: the Hannibal Lecters of the world who seem calm and controlled as they torture, scheme and kill. Psychopathy is marked by a total lack of empathy with others, allowing them to act without compunction. The rare cases of acquired sociopathy, where brain damage leads to behavioural patterns that resemble the psychopath, are perhaps even more unsettling. It's one thing when it's the other guy - born different. But the acquired case holds the terrifying promise that it could be you.

While we shiver at the horridness of all this, scientists have leapt at the chance to study these individuals in the hope that it may shed some light on whether we have a design for violence. As with much research, the exception helps you find the rule: the differences in the psychopaths' brains and behaviour give insights into what is shaping the behaviour of normal people. One thesis that has gained broad popular attention (to which popular science writer Steven Pinker devotes a chapter of his recent book The Blank Slate) is that cases of violence running wild illuminate the caged beast inside all of us. This account argues we have inclinations towards violence only barely kept in check by imposed restraints; not dissimilar to a popular religious notion that humanity is fallen from grace -urged to good but drawn to evil.

It seems true that abnormal populations differ from us because they lack some kind of restraint: some failure of an inhibition mechanism which ordinarily screens out or rejects violent actions in healthy individuals. James Blair, a leading researcher in this area, has termed this a Violence Inhibition Mechanism (VIM, see e.g. Blair & Cipolotti 2000): and follows early ethological work showing that some animals in the wild cease their aggression if their victim shows signs of distress (Lorenz, 1966). Evolutionary pressure could promote such a tendency to discourage fighting to the death, switching you off from pursuing a conflict once your opponent caves in.

Other researchers point more generally to the role that the frontal lobes of the brain play in inhibition of inappropriate behaviour, suggesting that problems with these regions lead to the failure to inhibit violent acts. The two explanations may not be exclusive, but the inhibition-frontal lobe thesis is primarily investigated in acquired cases, whilst the VIM is researched in developmental cases. The upshot is that proponents of a deep and negative human nature argue that as we are engaging in suppression, there must be something there to suppress - therefore, there is violence within us. For example, Steven Pinker (2002) states that “direct signs of design for aggression” include the fact that “disruptions of inhibitory systems...can lead to aggressive attacks” (p316).

But this conclusion is premature in principle, and not supported in practice. Firstly, the principle. The argument that we can judge our inclination to violence by observing it in a free situation is flawed because it doesn't take base rates into account. By base rates, I mean what our level of violence would be if we were `violence blind': if we had no interest, but no disinterest, in whether our actions caused harm.Science fiction author Isaac Asimov recognised that this rate would not be zero, and made this a key concept in his Robot trilogy, the First Law of Robotics. This was the rule which trumped all others, and commanded that "A robot may not injure a human being, or, through inaction, allow a human being to come to harm."The robots are not given this rule to counteract some kind of 'assassination chip' placed there by a mischievous designer, but simply to act as a guiding principle to distinguish certain kinds of actions into acceptable and unacceptable. Asimov saw that you would need an inhibition system in place even when there is no tendency to cause harm; without specifications, harm will tend to occur. Without establishing fully what such a base rate would be, it is absurd to look at the harm any individual causes and conclude this is evidence for violence worked into the design.

When we turn to the evidence, violence for its own purpose does give a good account of the actions of these patients. For example, Blair and Cipolotti (2000) describe a patient with frontal lobe damage whose use of violence was goal-directed, for the purpose of excitement (pushing another resisting patient around in a wheelchair at speed) or to protest when frustrated. This does not resemble the sating of a wild hunger for aggression, but is more like a slide towards the base-rate – uncaring that your desires have harmful consequences.

It is difficult to see how someone could seriously advance the perspective that we are innately violent - commit violence far in excess of the base rates. Even considering the bloodiness of human history (and leaving apart the social factors underpinning conquest and genocide), the potential bloodshed from the base rate is equally boggling. Moreover killing for the sake of it would be inefficient, and considering our basis as a social species would be utterly foolish, so it makes good evolutionary sense that we are not drawn to violence.

So let's retreat a little: perhaps the issue isn’t innate violence, despite the rhetoric; perhaps the argument is that we're not averse to using violence, that we use it when it pays, much like we would do if we used the base rate. This is an issue that evolutionary psychology often investigates, modeling factors to uncover in which situations it would pay us to commit harmful acts (such as to revenge a slight in a culture of honour (Cohen, Nisbett, Bowdle, & Schwarz. 1996). All very well, if proving very little about violence in the brain. But however productive this line of research is, even this weak version finds a fairly big stumbling block, in the very phenomena we began with: the existence of systems that work to inhibit violence.

We took aside these inhibition systems (i.e. looked at neurological patients with damage to the areas that they reside in) in order to say “let’s look at what’s really going on.” But whilst this approach can tell us useful things, we need to put it all back together again: what makes us human isn't just what lies beneath our inhibition systems, but is the fact that we inhibit at all, in such a sophisticated and complex manner. This is what renders the quote from Pinker so empty: the inhibition system itself is a product of design.

Anyone doubting that treating other people as more than instruments is founded in the brain would do well to look into developments in the study of self–other mapping. This has provided stronger and stronger evidence that these relationships are hardwired into us, strikingly with the discovery of mirror neurons that fire in the same way for events that occur to you or to those you observe (Gallese and Goldman 1998). Many argue that empathy is an outcome of these representations (see e.g. Frith and Frith 1999). And recent research demonstrates appreciating someone else's pain activates many of the same areas as experiencing it (Jackson, Meltzoff, & Decety 2004): good evidence for a VIM-like mechanism, and certainly a rebuttal to those who think our withdrawal from violence is unnatural.

By making psychopaths into poster-boys for innate violence, we risk ignoring crucial aspects of their behaviour. The patients investigated by Blair and Cipolotti were reported as socially inappropriate in a variety of ways, and recent imaging work suggests that the areas crucial for regulating and preventing aggression also keep us within the bounds of socially acceptable behaviour (Berthoz, Armony, Blair, & Dolan, 2002). Rehabilitation would require addressing that big picture.

Designed for violence? Really, the strongest conclusion that this work can give is that we sometimes are violent when it's in our interests. We are not innately disposed to violence, or even indifferent to violence, we are neurologically bound away from violence. This understanding gives us a solid basis for treatment, and an honest beginning from which to address the continuing problem of violence in society.